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4A-GE bluetop pistons & rods into a 4A-FE = kaboom?

10K views 15 replies 4 participants last post by  Evo_lucian 
#1 · (Edited)
Couldn't find a topic from searching, here or elsewhere. Just wondering if it's feasible to run a 4A-FE on the stock computer with the 9.4:1 4A-GE pistons & rods on the 4A-FE crank? FE crank is supposed to have 40mm rod journals, just like the early GE crank.

I'm guessing there might be problems with interference? I know that the GE piston dome & the FE combustion chamber don't have the same shape. I'm curious about this because sometime soon I will need to pull my motor & tranny/transfer case to change out the clutch / pp / resurface the flywheel. (I have a 4A-GE build slowly going at the moment, but I want to break in its clutch before the engine swap.) I have a set of bluetop pistons & rods sitting in a box. I could clean them up, get some new rings & bearings, and do a minor rebuild of the FE while it's out.

Crazy idea I know... it is 3am right now and I need to get some sleep. :lol: :ugh3:

Other thought is, I have a set of pistons (and bad/bent rods) from a 1997 4A-FE sitting in my garage. Could I throw those pistons onto the bluetop rods (same 18mm press-fit pin, I believe) into my 1988 4A-FE and see an increase in compression? I can't remember the reason for Toyota's redesign of the FE pistons for the '93-'97 years.
 
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#3 ·
it would be more around 12-13.... the combustion chamber volume in a 4afe is significantly smaller than a 4age and is why the 4afe pistons are dished.

I my guess would be that there's high possibility of valve clearance issues using the 4age pistons with the 4afe head.
 
#4 ·
Thanks guys. Someone else told me he thought it would be more like 10.5:1. He's gone through the process of rebuilding a 4A-FE for more output, though he used 4A-GZE pistons to bump up the compression a little.

bluetop pistons in a 4af application would raise the static CR to about 10.5 to 1. The std camshaft for the early F head is very short duration... 10.5 CR and a short duration camshaft might be too high a DCR... and so it could cause ping. A bit more duration(10 degrees maximum) might be useful.
DCR = dynamic compression ratio, something I need to read up on when I have the time (for my main build)...
 
#7 ·
I have done many things that a lot of the "experts" said couldn't be done . I say f@ck it ! Go ahead and do it. I did a 10.8:1 c/r 4agze with stock ecu on 4ag pistons on 91 octane, zero problems. If you have any pinging issues on 93 octane ( I highly doubt you will) just retard the ignition timing a degree or 2 at the distributor.
 
#8 · (Edited)
Thanks for the input... now I'm just wondering what the 1 point bump in compression will do. Increase torque & HP a little bit? Not too worried about MPG since I already get semi-crummy mileage from pushing the FE motor to "go faster" limits (though not redlining). If this works, it would be great for others to copy & get a little more out of the 4A-FE.

I'll definitely get new bearings, but do you think I should get new rings & wrist pins?


Edit: I suppose this idea would work best with "supporting mods" like 2¼" exhaust, custom or aftermarket header, etc.
 
#9 ·
While you at it a new set of rings would be a good idea, they only $30. If the wrist pins are in good shape, no need to change them.

With the increase in compression you will get a slight increase in torque and hp . How much ? I cannot tell you. I can just say my 4agze pulled like nothing I have ever seen.

Exhaust is not really needed with just a compression bump but if you got the $ then go ahead and do it .
 
#10 ·
Couldn't find a topic from searching, here or elsewhere. Just wondering if it's feasible to run a 4A-FE on the stock computer with the 9.4:1 4A-GE pistons & rods on the 4A-FE crank? FE crank is supposed to have 40mm rod journals, just like the early GE crank.

I'm guessing there might be problems with interference? I know that the GE piston dome & the FE combustion chamber don't have the same shape. I'm curious about this because sometime soon I will need to pull my motor & tranny/transfer case to change out the clutch / pp / resurface the flywheel. (I have a 4A-GE build slowly going at the moment, but I want to break in its clutch before the engine swap.) I have a set of bluetop pistons & rods sitting in a box. I could clean them up, get some new rings & bearings, and do a minor rebuild of the FE while it's out.

Crazy idea I know... it is 3am right now and I need to get some sleep. :lol: :ugh3:

Other thought is, I have a set of pistons (and bad/bent rods) from a 1997 4A-FE sitting in my garage. Could I throw those pistons onto the bluetop rods (same 18mm press-fit pin, I believe) into my 1988 4A-FE and see an increase in compression? I can't remember the reason for Toyota's redesign of the FE pistons for the '93-'97 years.
Which gen 4afe are you going to put the bluetop piston on?
 
#12 ·
oh thats cool to see someone still experimenting with the 1st gens, but if your putting bluetop pistons on a 1st gen 4AFE and it runs well it should work for the 4A-F as well right? Since there both the samething just one is EFI.

When you can I would like to see some pic's of your build.
 
#15 ·
OK, thanks. Whenever I have my 4A-FE pulled out, I will verify so everyone can know.

I think the '97 FE rods I have use a press-fit 20mm wrist pin, but have 40mm big ends. I will have to double check & edit this post.

Another thing I'm wondering about... stupid question time. Are the F/FE and GE cams interchangeable? I'm wondering why Web Cams shows the same grinds (like the 294 grind) for both engines. I thought they were different, mostly because the intake cam is slaved to the exhaust cam in an F/FE. Curious because I'm planning to get a set of #294 for my GE build.
 
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